TILI Automation

 Explain why the direction of flow shown in the below image goes from left to right. What would happen if we sent fluid flow through this control valve in reverse direction i.e. from right to left instead? Fluid Flow Reversed through Control Valve If we were to use this valve “backwards,” the pressure drop across the plug would tend to “slam” it closed whenever it approached the closed position. In other words, the process fluid’s differential pressure drop would make it very difficult to maintain any plug position near full-closed. This is actually an example of a mechanical feedback system. As the valve closes, the pressure drop across it (in most processes) usually rises because other pressure losses in the piping system decrease with decreased flow, leaving the valve to drop all the fluid pressure. Since plug position has an effect on pressure drop, and pressure drop exerts a mechanical force on the plug, there is a system of feedback at work here. In the proper flow direction, the feedba...

 The purpose of proof testing is to detect the failures within the transmitter that are not detected by the regular diagnostics of the transmitter. Of main concern are undetected failures that prevent the safety instrumented function from performing its intended function. Proof Testing Method The frequency of the proof tests (or the proof test interval) is to be determined in the reliability calculations for the safety instrumented functions for which the transmitter is applied. The actual proof tests must be performed more frequently or as frequently as specified in the calculation in order to maintain the required safety integrity of the safety instrumented function. The following tests need to be specifically executed when a proof test is performed. The results of the proof test need to be documented and this documentation should be part of a plant safety management system. Failures that are detected should be reported to the manufacturer. The personnel performing the proof test...

 n this post, we will study the concept of the Modbus ASCII protocol. Modbus is a communication protocol that is widely used in PLCs. It is a type of serial communication. Nowadays, apart from PLC’s, it is widely used in various ranges of instruments like PID controllers, sensors, various types of electronic instruments, VFD’s, etc. Modbus works in master-slave mode. That means, suppose there is a PLC that acts as a master and three VFD’s which act as slaves. If you understand it in simpler terms, it is a turn-by-turn protocol. The PLC requests information from the first slave; then the second slave and at last, the third slave. It requests for data in a set period of time; and if the response is not received (timeout time), then it proceeds for the next slave and so on. After the last slave, it goes back again to the first slave. Also, apart from reading, it also writes data to slaves one by one. MODBUS ASCII Communication Protocol Modbus works on three hardware layers for serial ...